package algorithm.leetcode;

public class Num110 {

    public static void main(String[] args) {
        TreeNode root = new TreeNode(3);
        root.left = new TreeNode(9);
        TreeNode right1 = new TreeNode(20);
        right1.left = new TreeNode(15);
        right1.right = new TreeNode(7);
        root.right = right1;
        System.out.println(root);
        System.out.println(isBalanced(root));
    }

    public static boolean isBalanced(TreeNode root) {
        if (root == null) {
            return true;
        }
        return helper(root) != -1;
    }

    private static int helper(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = helper(root.left);
        int right = helper(root.right);
        if (left == -1 || right == -1
                || Math.abs(left - right) > 1) {
            return -1;
        }
        return Math.max(left, right) + 1;
    }
}
